1
Praxis 5442 - Physical Science Questions and Answers Latest Version Graded A+
What is the primary reason gases expand to fill their container?✔✔Gas particles move randomly and have negligible intermolecular forces
What happens to the pressure of a gas when its volume is halved at constant temperature?✔✔The pressure doubles
What does the ideal gas law describe?✔✔The relationship among pressure, volume, temperature, and number of moles of gas
What is the unit of the gas constant R when using pressure in atm and volume in liters?✔✔0.0821 L·atm/mol·K
What type of process is described by a constant temperature change in a gas?✔✔Isothermal process 1 / 4
2
Why does increasing temperature increase the rate of a chemical reaction?✔✔More particles have sufficient energy to overcome the activation energy barrier
What is the activation energy of a reaction?✔✔The minimum energy required to start a chemical reaction
Why do chemical reactions generally occur faster in the gas phase than in the solid phase?✔✔Particles move more freely and collide more often in the gas phase
What is enthalpy?✔✔The total heat content of a system at constant pressure
What does a negative ΔH value indicate in a chemical reaction?✔✔The reaction is exothermic
What is the main difference between an endothermic and an exothermic process?✔✔Endothermic absorbs heat; exothermic releases heat 2 / 4
3
What does Le Chatelier’s Principle predict about a system at equilibrium when pressure is increased?✔✔The system will shift to the side with fewer gas molecules
Why does adding a catalyst increase the rate of a reaction?✔✔It lowers the activation energy required for the reaction
What property of a gas is directly proportional to its temperature in Kelvin?✔✔Kinetic energy of the gas particles
What is the effect of decreasing the temperature on an endothermic reaction at equilibrium?✔✔It shifts the equilibrium to the left (toward reactants)
Why does water have a higher boiling point than methane?✔✔Water forms hydrogen bonds, which are stronger than the dispersion forces in methane
What is entropy? 3 / 4
4
✔✔A measure of the disorder or randomness in a system
What happens to entropy when a solid turns into a gas?✔✔Entropy increases
Why does a balloon shrink when placed in a freezer?✔✔Gas particles move slower, reducing internal pressure and volume
What is the relationship between intermolecular forces and boiling point?✔✔Stronger intermolecular forces result in higher boiling points
What does the collision theory of reaction rates state?✔✔Reactions occur when particles collide with proper orientation and sufficient energy
Why does increasing surface area increase the rate of a solid reacting with a liquid?✔✔More surface is exposed, allowing more collisions between reactants
What is the standard state of a substance?
- / 4